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# Physics practical on electricity, and precaution

Physics practical on electricity

If you are a student preparing for exam, this is for you or maybe you are a teacher trying to refresh your brain before going to class, this is also very useful to you.

This physics practical on electricity is going to teach you the relationship between resistance, current and potential difference as stated by ohms law.

Let take it that the  circuit is connected as shown above.  In this circuit you are to determine the current as we vary the resistance in the resistance box.

Take e.m.f of the battery as 1.5V for this physics practical on electricity.

Set the resistance at the resistance box to R=OΩ

Close the key and

Read the current I, at ammeter A in the circuit above

Repeat the procedure with R2, R3, R4 , R5 R6, This is done by adjust resistance in resistance box  to R1, R2, R3, R4, R5 and R6 and obtaining the corresponding I1, I2, I3, I4, I5 and I6  from ammeter A  reading ,respectively .

Record the value of R1, R2, R3, R4, R5 and R6

Record the value of current I1, I2, I3, I4, I5 and I6

After this you are done with you physics practical on electricity, what is remaining is the follow up questions

Let assume that the reading of resistance and the current are represented by the diagrams below

In above diagram the active resistance is the one that is not painted while the painted one is not active.

Therefore from this diagram, resistance R1 = o, R2 =1, R3 = 2 R4 = 3, R5 = 4 and R6 = 5.

Ammeter

From the diagrams above you can take your reading and make a table as shown below

Reading from the diagram above shows that, I1= 3.00, I2.00 =1,  I3 =0.60,  I4= 043,  I5=0.33, and I6 =0.27

NOTE: When you are writing experimental value put it in two decimal places, If it is a worked value, it can be in three decimal place.  And also note that, they must be in uniform decimal places, so you cannot put one  in two decimal places, and the other in three or more.

From what we got from resistance box and the Ammeter we can make this table below.

Follow up questions on physics practical electricity

1. Evaluate P =E/I and make a table of I, R, and p

2. State the precaution you would have used if you were performing this experiment in laboratory

3. Define the internal resistance of the cell

4. A cell of e.m.f 4.5V is connected across a resistor of resistance 4Ω. If a current of 0.9A passes through the circuit, calculate the internal resistance of the cell.

1.  P= E/I

When E =1.5 and I 0.27, p = 1.5/0.27 =6.o

2. Precautions used in physics practical on electricity above.

(a) I made sure that the key is removed or not closed when I was not taking the reading

(B). I ensured tight connections

(C) I ensured that the terminals are clean before connection

(D). I avoided the zero error of ammeter.

Please while listing the precautions, do not use present or future tense, but use past tense as I did above. Fellow to do that may attract no mark or penalty.

3. Definition of internal resistance

Internal resistance is the resistance of cell when is not delivering any current. Or opposition to the flow of current offered by the cell itself.

4. Calculation of internal resistance when, e.m.f of the cell is 4.5V, resistance = 4Ω, and the current =0.9A

Using    I = E/R + r    where r = internal resistance, therefore

(R + r)I = E

IR + Ir = E

Ir=E-IR

r= E-IR/I

E-IR = 4.5 – 0.9 x 4 =4.5 – 3.6 = 0.9, then

r =0.9/0.9 = 1Ω 